The human retinal contains three types of cones, red cones sensitive to long wavelength (red range), green cones sensitive to middle wavelength (green range) and blue cones sensitive to short wavelength (blue range). It is thought that, upon light entering the eye, the cones respond to the light to allow us to recognize colors according to red wavelength, green wavelength and blue wavelength of the incoming light. The color recognition differs depending on the sensitivities of the three types of cones, that is, color vision properties. For example, a person having a lower sensitivity of red cones sensitive to a red range recognizes colors with less red component. Therefore, the difference between the red color and the brown color in the scenery that the person is looking becomes hard to discern. As described above, color perception varies from person to person.
For this reason, as a color-vision assist device designed for persons with less ability to identify colors such that they can perceive the same colors of the scenery as those perceived by persons with standard visual sensitivity, Patent Literature 1 discloses the configuration “including: a color camera taking outside pictures and generating image data for each color; a lookup table storing input/output characteristics for each color in image data; a multiplier for amplifying the output of the lookup table at a preset gain; a display assembly for reproducing the multiplier output in an image; and a projection lens for projecting the image reproduced by the display assembly on a pupil, in which the image data for each color obtained by the shooting is converted to image data made available to a wearer for easy color discrimination, for display (excerpts from abstract)”.